How is AraC operon regulated?
How is AraC operon regulated?
The ara operon is regulated by the AraC protein. If arabinose is absent, the dimer AraC protein represses the structural gene by binding to araI1 and araO2 and the DNA forms a loop, which prevents RNA polymerase from binding to the promoter of the ara operon, thereby blocking transcription. This breaks the DNA loop.
What is the role of the AraC gene?
The araC gene encodes a positive regulatory protein required for L-arabinose utilization in Escherichia coli. This work describes the identification of the region of the araC promoter that interacts with the cAMP receptor protein to mediate catabolite repression.
What is AraC in biology?
From Wikipedia, the free encyclopedia. AraC may refer to: The araC gene and AraC protein, components of the L-arabinose operon in the genome of the bacterium Escherichia coli. Cytarabine, (also known as cytosine arabinoside (ara-C)) a chemotherapeutic agent commonly used in the treatment of leukemias and lymphomas.
Is AraC a repressor or inducer?
For example, the widely used AraC transcription factor of the arabinose operon acts as a repressor in the absence of its cognate inducer arabinose and as an activator in the presence of arabinose (Ogden, Haggerty, Stoner, Kolodrubetz, & Schleif, 1980).
Is AraC constitutively expressed?
This shows that the arm residues play a major role in the immobilization of the DNA binding domains that is required for repression. According to the light switch mechanism, when the domains cannot be immobilized, AraC by default activates transcription, and the result is constitutivity.
Is AraC a positive regulator?
Autoregulation of AraC The expression of araC is negatively regulated by its own protein product, AraC.
Is AraC a gene or DNA sequence?
The DNA sequence of the araC gene of E. carotovora was 58% homologous to that of E. coli and 59% homologous to that of S. typhimurium, with respect to the common region they share.
What is unique about the AraC protein’s role in regulation of the arabinose operon?
The regulator protein AraC is sensitive to the level of arabinose and plays a dual role as both an activator in the presence of arabinose and a repressor in the absence of arabinose to regulate the expression of araBAD.
Which of the following mechanism is operated by the AraC regulatory protein?
The AraC regulatory protein controls the transport and metabolism of the 5-carbon sugar arabinose. When arabinose binds to AraC, it converts it from a repressor to an activator.
How does the AraC regulatory protein turn on transcription in the presence of arabinose?
(a) In the presence of arabinose, the AracC protein binds to the araI region and, when bound to cAMP, the CAP protein binds to a site adjacent to araI. This stimulates the transcription of the araB, araA, and araD genes.
How does the AraC protein regulate its own synthesis?
AraC protein regulates expression of its own synthesis9 and the other genes of the ara system. AraC protein shifts from the state of preferring to loop DNA (when arabinose is absent) to the state of preferring to bind to adjacent DNA half-sites (when arabinose is present).
Where does arabinose bind to the AraC operon?
Arabinose converts the repressor form of AraC to the activator form to regulate the araBAD promoter (PubMed: 2962192, PubMed: 3279415 ). In the absence of arabinose, AraC binds to the araO2 and araI1 half-sites in the promoter region of the araBAD operon, leading to the formation of a DNA loop that blocks access of RNA polymerase to the promoter.
How is AraC used as a positive control?
Native AraC cloned under the same constitutive promoters was used as a positive control (AraC WT ). The bars for AraC represent the values obtained without (gray) and with 0.1% (orange) arabinose for 4 h.
What are the regulatory features of the ara operon?
Regulatory control features of the ara operon. Sites for RNA polymerase (RNAP), AraC, and cyclic AMP repressor protein (CRP) binding within the ara control region are shown schematically.
